Reading Data

EoReader provides a cursor over a caller-owned byte buffer and exposes methods for reading EO-encoded values. The reader does not take ownership of the underlying data.

Basic usage:

// Data buffer owned by the caller.
const uint8_t *buf = ...;
size_t buf_len     = ...;
 
EoReader reader = eo_reader_init(buf, buf_len);
 
int32_t action;
int32_t family;
if (eo_reader_get_byte(&reader, (uint8_t *)&action) != EO_SUCCESS ||
    eo_reader_get_byte(&reader, (uint8_t *)&family) != EO_SUCCESS) {
    // handle error
}
 
int32_t player_id;
eo_reader_get_short(&reader, &player_id);
 
char *name = NULL;
eo_reader_get_string(&reader, &name);
// ... use name ...
free(name);

Chunked reading mode:

EO packets use 0xFF bytes as chunk delimiters. Enable chunked reading mode to respect these boundaries automatically. While in chunked mode, eo_reader_remaining() and all get_* functions operate only within the current chunk. Call eo_reader_next_chunk() to advance past the next 0xFF delimiter.

EoReader reader = eo_reader_init(buf, buf_len);
eo_reader_set_chunked_reading_mode(&reader, true);
 
// Read fields from the first chunk.
int32_t val;
eo_reader_get_char(&reader, &val);
 
// Advance to the second chunk.
eo_reader_next_chunk(&reader);
char *str = NULL;
eo_reader_get_string(&reader, &str);
free(str);

Number types and their byte widths:

Function	Bytes read	Max value
eo_reader_get_byte()	1	255
eo_reader_get_char()	1	EO_CHAR_MAX
eo_reader_get_short()	2	EO_SHORT_MAX
eo_reader_get_three()	3	EO_THREE_MAX
eo_reader_get_int()	4	EO_INT_MAX

Negative numbers:

EO number encoding is not sign-aware. eo_reader_get_int() decodes the four EO bytes into a 32-bit bit pattern and returns it as int32_t.

For values in the range [0, INT32_MAX], this behaves like an ordinary positive integer read. When the decoded 32-bit pattern is at least 2^31, the returned int32_t becomes negative on typical two's-complement systems.

For example, the EO bytes A8 B5 9A 85 decode to the bit pattern 2147483648, which is returned as INT32_MIN.

Only 4-byte EO ints can produce negative results this way. eo_reader_get_char(), eo_reader_get_short(), and eo_reader_get_three() always return non-negative values because their decoded ranges never reach the sign bit.